New building materials

Multi Walled Carbon Nanotube

The Building Societies Association (BSA) published a report on 17th November, recommending off-site construction as its answer to the UK housing shortage [1], an option previously explored by Rockfire in an article on 1st November. The BSA seems anxious to stress that modular, factory-built housing is now much more than just a means of providing a quick fix to a problem of volume. It is a high quality solution far removed from the post-war prefabs of popular belief.

There is certainly a residual admiration among Britons for old houses despite the fact that they are often cold and inconvenient. This in turn can translate into a cultural suspicion that modern houses might not be built to last. But the construction industry is proving particularly resourceful in finding new applications for materials that have been developed to meet needs in sectors from biomedicine to aerospace and many of these look more durable by far than traditional bricks and mortar.

The best known of these is probably graphene, the de facto material of choice if it’s strength you are after. One hundred times stronger than steel, it is also a good conductor of heat and electricity and its potential uses include solar cells and electric circuitry among many others.

Aerogel has actually been around since 1931 and is more solid than it might sound. Despite being almost weightless, with just 1.8% of its mass made up of gels and the rest of air, its structure is strong. It is a poor conductor of heat and has been used by NASA for the thermal insulation of space suits. It is virtually transparent so could be a wonderful insulation material for buildings were it not so expensive at present. But that may change.

Self-healing concrete is another triumph of ingenious DIY over costly maintenance contracts. It occurred to Hendrik Jonkers from Delft, that limestone-producing bacteria might generate a sort of natural grouting polyfilla inside concrete structures. If the concrete cracks, his bacteria, embedded into the structure in biodegradable capsules, are released as they come into contact with water and start to operate an on-site limestone production process, filling the grooves automatically. Fortunately for Mr Jonkers and proprietors of concrete structures, he has managed to find not one but two limestone-producing bacteria that are able to survive for 50 years without food or oxygen and which seem suitable for long-term encapsulation.

Other fascinating new materials draw directly from nature or are inspired by it. Hempcrete and ferrock are naturally-occurring, CO2-absorbing alternatives to brick, insulation and concrete. Mycelium from fungi has been used to make a durable but biodegradable brick. To add to recycled plastic components, there are now bioplastic components made from shrimp shells. Synthetic spider’s webs emulate one of nature’s strongest threads and “sweaty” rooftops hang on to rainfall until it is required. Elon Musk has just produced a range of solar PV roof tiles that look as though they have been baked from Mexican earth and there are wonderful kinetic floors such as those made by Pavegen whose tiles generate seven watts of energy per footstep.

It is already possible to build a house with a zero carbon footprint by combining different elements of which the above are but a sample. Perhaps more interesting still is the work of designers at Cardiff University who managed to build such a house, in just 4 months, for an economical £1000/m2 which is the upper threshold budgeted for social housing.

[1] Laying the foundations for MMC
[2] Designers create the ‘impossible’ zero-carbon house